The authors would like to acknowledge the University of Colorado Boulder for its support of this work.

ATENÇÃO: Muitos dos produtos químicos utilizados neste protocolo são substâncias perigosas. Consulte Fichas de Segurança (MSDS) e usar equipamento de proteção individual (EPI) quando se trabalha com essas substâncias. 1. Purificação, preparação e armazenamento dos Reagentes <ol><li> Purifica-se todos os solventes a serem utilizados com um sistema de purificação do solvente de acordo com o protocolo do fabricante. Se um sistema de purificação de solvente não está disponível, utilizar agentes de secagem (por exemplo, peneiros moleculares, CaH 2, etc.) e destilação. Uma vez secos, armazenar os solventes sob atmosfera de azoto na caixa de luvas, à temperatura ambiente. </li><li> Purifica-se todos os monómeros por destilação sob vácuo de acordo com o protocolo do fabricante. Uma vez destilado, armazenar os monómeros em frascos escuros sob atmosfera de azoto num frigorífico. </li><li> Purifica-se iniciadores por destilação sob vácuo de acordo com o protocolo do fabricante. Uma vez destilado, loja iniciadores emgarrafas escuras sob atmosfera de azoto no frigorífico. </li><li> Purifica-se o perileno por sublimação de acordo com o protocolo do fabricante. Uma vez sublimado, armazenar o perileno da bancada à temperatura ambiente. </li><li> Prepara-se uma solução de 250 ppm de hidroxitolueno butilado (BHT) em clorofórmio deuterado (CDCl3) pela adição de 25,0 mg de BHT para um frasco de 100 g de CDCl3. Preparar e armazenar esta solução na bancada. </li></ol> 2. A fotopolimerização de Metacrilato de Metilo Utilizando Perileno como o fotocatalisador <ol><li> Permitir que todos os reagentes atinjam a temperatura ambiente. Inspeccionar todos os reagentes antes da utilização para assegurar que não há sinal de contaminação, tais como descoloração ou de formação de partículas sólidas. </li><li> Em uma atmosfera de azoto porta-luvas, coloque uma pequena barra de agitação em um frasco de cintilação de 20 ml. Adicionar 2,36 mg (9,38? Mol, 1,00 eq.) De perileno. </li><li> Adicionar 1,00 ml de dimetilformamida (DMF). </li><li> A esta mistura, adicionar 1,00 mL (9,38 mmol,1,000 eq.) De metacrilato de metilo (MMA). </li><li> Colocar o frasco numa placa de agitação ajustado para 1600 rpm e iluminado por tiras de diodos emissores de luz branca (LED). Limitar qualquer iluminação de outras fontes de luz (por exemplo, luzes do teto, janelas próximas). </li><li> Para iniciar a reacção, adicionar 16,4 mL (93,8 mol, 10,0 eq.) De acetato de etilo-bromofenil α (EBP) através de uma pipeta. Nota: Para executar esta reacção usando a luz solar natural, siga os passos acima, ignorando etapa 2.5, em seguida, selar o frasco, trazê-lo para fora do porta-luvas, e coloque o frasco em uma área iluminada pela luz solar natural. </li><li> Agita-se a mistura reaccional durante 24 h sob uma iluminação constante. Isolar e purificar o produto poli (MMA), seguindo as instruções em passos 4,1 - 4,4. </li></ol> 3. Cinética A análise da reacção <ol><li> Na bancada, dispensar 0,70 ml de BHT em CDCl3 solução para um frasco de 2 ml e vedar com uma tampa de septo. Traga esta i frasco<html> nto da caixa de luvas em que a polimerização se realiza. </li><li> Utilize uma seringa para remover 0,20 ml da mistura de reacção. Injectar o conteúdo da seringa no frasco de 2 ml contendo a solução de 250 ppm de BHT em CDCl3. Retire-se e empurrar o êmbolo em várias vezes para assegurar a extinção completa da polimerização. </li><li> Transferir o conteúdo do frasco de 2 ml a um tubo de espectroscopia de RMN (ressonância magnética nuclear). Analisar esta amostra através de 1 H espectroscopia de RMN para a conversão por cento. 24 </li><li> Para o exemplo específico da polimerização de metacrilato de metilo usando perileno, calcular a percentagem de conversão a partir do espectro de 1 H RMN da amostra por comparação da área sob o pico correspondente aos hidrogénios de metoxi de o monómero que não reagiu (δ = 3,62) (H) e o área sob o pico correspondente aos hidrogénios de metoxi de o polímero (δ = 3,50) (P) com a seguinte fórmula: 1 &quot;src =&quot; / files / ftp_upload / 53571 / 53571eq1.jpg &quot;/&gt; </li><li> Após análise, verter o conteúdo do tubo de espectroscopia de RMN num frasco de cintilação de 20 ml limpo. Evapora-se o solvente sob pressão reduzida. Re-dissolver a amostra em 1,00 ml de tetra-hidrofurano (THF). </li><li> Enviar a amostra através de um filtro de seringa em um limpa frasco de 2 ml. Analisar a amostra por meio de cromatografia de permeação em gel (GPC) acoplado com multi-ângulo de dispersão de luz para determinar o peso molecular médio em número (Mn), o peso molecular médio em peso (M w), e dispersividade (DJ). 24 </li></ol> 4. Isolamento e purificação do produto polimérico <ol><li> Extingue-se a reacção de polimerização, vertendo o conteúdo da mistura de reacção num excesso de 50 vezes de metanol e deixando-se agitar durante pelo menos 1 h. </li><li> Isolar o poli (metacrilato de metilo) a partir do metanol por filtração sob vácuo de acordo com o fabricante doprotocolo. Nota: O método de isolamento pode variar dependendo do polímero produzido. Para poli (metacrilato de metilo) e poliestireno, filtrar a vácuo o polímero precipitado a partir do metanol utilizando um funil de Buchner. Para poli (acrilato de butilo), decanta-se o metanol a partir do polímero viscoso. </li><li> Lavar o polímero com um adicional de 100 ml de metanol. </li><li> Re-dissolver o polímero em diclorometano e repita os passos 4.1 até 4.3, duas vezes. </li></ol> 5. de extensão de cadeia de um macroiniciador MMA com estireno para produzir partículas de poli (MMA) -b-poli (S) <ol><li> Permitir que todos os reagentes atinjam a temperatura ambiente. Inspeccionar todos os reagentes antes da utilização para assegurar que não há sinal de contaminação, tais como descoloração ou de formação de partículas sólidas. </li><li> Na caixa de luvas uma atmosfera de azoto, colocar 136 mg (2,34? Mol, 1,00 eq.) De poli (MMA) macroiniciador para um frasco de cintilação de 20 ml equipado com uma pequena barra de agitação. </li><li> Adicionar 0,59 mg perileno (2,34 mol, 1,00 eq.). </li><li> Adicionar 1,00 ml de DMF. </li><li> Colocar o frasco numa placa de agitação ajustado para 1600 rpm e iluminado por tiras de LEDs brancos. Limitar qualquer iluminação de outras fontes de luz (por exemplo, luzes do teto, janelas próximas). </li><li> A esta mistura, adicionar 1,24 mL (11,7 mmol, 5,000 eq.) De estireno (S) através de uma pipeta. </li><li> Agita-se a mistura reaccional durante 24 h sob uma iluminação constante. Isolar e purificar o produto poli (MMA) -b-poli (S), seguindo as instruções em passos 4,1 - 4,4. </li></ol>

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The authors have nothing to disclose.

Embora o protocolo demonstra um exemplo específico desta técnica de polimerização, as opções disponíveis ao investigador que executam esta reacção são bastante amplo. As modificações podem ser feitas a um número de pontos ao longo do protocolo, para permitir a optimização de qualquer photoredox nomeadamente PRTA está a ser executada. À medida que novos monómeros, iniciadores e catalisadores para esta reacção estão sob investigação, a estequiometria e solvente utilizado para realizar a reacção po...

The synthesis of technologically advanced polymers requires precise control over polymer molecular weight, dispersity (&#208;), composition, and architecture.1,2 Controlled radical polymerizations (CRPs)3-8 have revolutionized the synthesis of well-defined polymers, with atom transfer radical polymerization (ATRP) being the most used CRP, largely due to operational simplicity and synthetic versatility.9-14 The crux of ATRP is the ability to reversibly deactivate the polymerization, controlling the equilibrium between a propagating radical and a dormant species. Enforcing a low concentration of active radicals greatly minimizes bimolecular termination pathways and allows for the synthesis of well-defined polymers. 
Traditional ATRP relies on a transition metal catalyst to mediate this equilibrium.3 These metal catalysts contaminate the polymer product and impede implementation in biomedical or electronic applications while also raising environmental concerns. Although significant strides have been made to reduce the catalyst concentration to ppm levels, these methodologies require more demanding experimental conditions and metal contamination is still not entirely eliminated.15,16
Reversible addition-fragmentation transfer17,18 and nitroxide-mediated polymerizations19,20 are CRPs that do not require metal catalysts, although they have been used less often than ATRP.3 Recently, reversible chain-transfer21 and reversible complexation22,23 variants of ATRP that can use organic catalysts were reported. However, these methodologies require the use of alkyl iodide initiators and are not effective with the alkyl bromides commonly employed in ATRP. A highly desirable CRP would match the performance, feasibility, and robustness of traditional ATRP while being catalyzed by an organic catalyst under mild conditions.
Here, we describe a methodology for the radical polymerization of functionalized vinyl monomers using perylene as a visible-light photocatalyst. Through optimization of parameters such as stoichiometry, concentration, time, and light flux, the molecular weight of the polymers can be controlled.24, 25 Similar methodologies have been recently introduced using phenothiazine derivatives as photocatalysts for metal-free ATRP.26, 27 Because researchers in the field of polymerization catalysis are constantly developing new catalytic systems, the ability to compare catalyst performance across a number of metrics is vital. This ability to make comparisons relies heavily upon procedural consistency and clarity on the part of the researchers performing the experiments. As such, it is our goal that this video will be used to help precisely communicate the methods by which these polymers are synthesized and characterized.

<table><tbody><tr><td>perylene, min 98.0%</td><td>TCI America</td><td>TCP0078-025G</td><td>purify by sublimation</td></tr><tr><td>&lt;em&gt;N,N&lt;/em&gt;-dimethylformamide</td><td>VWR</td><td>EM-DX1726-1</td><td>Omnisolv</td></tr><tr><td>methyl methacrylate, 99%</td><td>VWR</td><td>200000-678</td><td>distilled prior to use, stored in refrigerator</td></tr><tr><td>ethyl &amp;alpha;-bromophenyl acetate&amp;nbsp;</td><td>Aldrich</td><td>554065</td><td>distilled prior to use stored in refrigerator</td></tr><tr><td>butylated hydroxytoluene&amp;nbsp;</td><td>Aldrich</td><td>W218405</td><td></td></tr><tr><td>Chloroform-D</td><td>Cambridge Isotope Labs</td><td>DLM-7-100</td><td></td></tr><tr><td>tetrahydrofuran</td><td>VWR</td><td>EM-TX0279-1</td><td>Omnisolv</td></tr><tr><td>methanol</td><td>VWR</td><td>BDH1135</td><td></td></tr><tr><td>dichloromethane</td><td>VWR</td><td>EM-DX0831-1</td><td>Omnisolv</td></tr><tr><td>styrene, 99%</td><td>VWR</td><td>AAAA18481-0F</td><td>distilled prior to use, stored in refrigerator</td></tr><tr><td>glass scintillation vial, 20&amp;nbsp;ml</td><td>VWR</td><td>66022-065</td><td></td></tr><tr><td>screw top vial, 2 ml</td><td>Agilent</td><td>5182-0715</td><td></td></tr><tr><td>septum cap for screw top vial</td><td>Agilent</td><td>5182-0717</td><td></td></tr><tr><td>heavy wall pressure vessel, 100 ml</td><td>Synthware</td><td>P160005&amp;nbsp;</td><td></td></tr><tr><td>syringe, 1 ml norm-ject</td><td>VWR</td><td>89174-491</td><td></td></tr><tr><td>NMR tube</td><td>New Era</td><td>NE-UL5-7&#039;</td><td></td></tr><tr><td>nylon syringe filter, 0.45&amp;nbsp;&amp;#956;m</td><td>VWR</td><td>28143-240</td><td></td></tr><tr><td>glovebox</td><td>Mbraun</td><td>LABstar</td><td></td></tr><tr><td>solvent purification system</td><td>Mbraun</td><td>MB-SPS-800</td><td></td></tr><tr><td>stirplate</td><td>IKA</td><td>3582401</td><td></td></tr><tr><td>light-emitting diodes</td><td>Creative Lighting Solutions</td><td>CL-FRS1210-5M-12V-WH</td><td>2x 12-inch strips of 5500 K white LEDs were used for illumination</td></tr><tr><td>12 V DC power supply for LEDs</td><td>Creative Lighting Solutions</td><td>CL-PS16001-40W</td><td></td></tr><tr><td>high performance liquid chromatograph&amp;nbsp;</td><td>Agilent</td><td>G1310B, G1322A, G1329B, G1316A</td><td></td></tr><tr><td>gel permeation size-exclusion columns</td><td>Agilent</td><td>PL1110-6500</td><td></td></tr><tr><td>multi-angle light scattering detector</td><td>Wyatt</td><td>WTREOS</td><td></td></tr><tr><td>differential refractometer</td><td>Wyatt</td><td>WTREX</td><td></td></tr></tbody></table>

atom transfer radical polymerization of functionalized vinyl monomers using perylene as a visible light photocatalyst

A standardized technique for atom transfer radical polymerization of vinyl monomers using perylene as a visible-light photocatalyst is presented. The procedure is performed under an inert atmosphere using air- and water-exclusion techniques. The outcome of the polymerization is affected by the ratios of monomer, initiator, and catalyst used as well as the reaction concentration, solvent, and nature of the light source. Temporal control over the polymerization can be exercised by turning the visible light source off and on. Low dispersities of the resultant polymers as well as the ability to chain-extend to form block copolymers suggest control over the polymerization, while chain end-group analysis provides evidence supporting an atom-transfer radical polymerization mechanism.

A Tabela 1 mostra o gama de resultados da polimerização alcançáveis ​​através deste método. Estes dados mostram que perileno é capaz de servir como um fotocatalisador para a polimerização de um certo número de monómeros de vinilo funcionalizados. Para um monómero específica, o ajuste de qualquer um de um número de parâmetros de reacção, tais como solvente, estequiometria, iniciador, e fonte de luz conduz a polímeros com diferentes pesos moleculares ...

Watch this Scientific Journal Video about Atom Transfer Radical Polymerization of Functionalized Vinyl Monomers Using Perylene as a Visible Light Photocatalyst at JoVE.com

Atom Transfer Radical Polymerization of Functionalized Vinyl Monomers Using Perylene as a Visible Light Photocatalyst

Polimerização Radical por Transferência de Átomos de Monômeros Vinílicos Funcionalizados Usando Perileno como Fotocatalisador de Luz Visível

A method for the atom transfer radical polymerization of functionalized vinyl monomers using perylene as a visible-light photocatalyst is described.

A standardized technique for atom transfer radical polymerization of vinyl monomers using perylene as a visible-light photocatalyst is presented. The ...

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Reactions of Alkenes

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11.6K visualizações.  University of Colorado Boulder. A method for the atom transfer radical polymerization of functionalized vinyl monomers using perylene as a visible-light photocatalyst is described.

Vídeo: Atom Transfer Radical Polymerization of Functionalized Vinyl Monomers Using Perylene as a Visible Light Photocatalyst

Reductive Electropolymerization of a Vinyl-containing Poly-pyridyl Complex on Glassy Carbon and Fluorine-doped Tin Oxide Electrodes

Controllable electrode surface modification is important in a number of fields, especially those with solar fuels applications. Electropolymerization is one surface modification technique that electrodeposits a polymeric film at the surface of an electrode by utilizing an applied potential to initiate the polymerization of substrates in the Helmholtz layer. This useful technique was first established by a Murray-Meyer collaboration at the University of North Carolina at Chapel Hill in the early 1980s and utilized to study numerous physical phenomena of films containing inorganic complexes as the monomeric substrate. Here, we highlight a procedure for coating electrodes with an inorganic complex by performing reductive electropolymerization of the vinyl-containing poly-pyridyl complex onto glassy carbon and fluorine doped tin oxide coated electrodes. Recommendations on electrochemical cell configurations and troubleshooting procedures are included. Although not explicitly described here, oxidative electropolymerization of pyrrole-containing compounds follows similar procedures to vinyl-based reductive electropolymerization but are far less sensitive to oxygen and water.

A procedure for performing reductive electropolymerization of vinyl-containing compounds onto glassy carbon and fluorine doped tin-oxide coated electrodes is presented. Recommendations on electrochemical cell configurations and troubleshooting procedures are included. Although not explicitly described here, oxidative electropolymerization of pyrrole-containing compounds follows similar procedures to vinyl-based reductive electropolymerization.

Electropolimerização redutiva de um complexo poli-piridil-vinil no Glassy contendo carbono e flúor-dopado com óxido de estanho Eléctrodos

Controllable electrode surface modification is important in a number of fields, especially those with solar fuels applications. Electropolymerization is ...

Química

Electroactive Polymer Nanoparticles Exhibiting Photothermal Properties

A method for the synthesis of electroactive polymers is demonstrated, starting with the synthesis of extended conjugation monomers using a three-step process that finishes with Negishi coupling. Negishi coupling is a cross-coupling process in which a chemical precursor is first lithiated, followed by transmetallation with ZnCl2. The resultant organozinc compound can be coupled to a dibrominated aromatic precursor to give the conjugated monomer. Polymer films can be prepared via electropolymerization of the monomer and characterized using cyclic voltammetry and ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy. Nanoparticles (NPs) are prepared via emulsion polymerization of the monomer using a two-surfactant system to yield an aqueous dispersion of the polymer NPs. The NPs are characterized using dynamic light scattering, electron microscopy, and UV-Vis-NIR-spectroscopy. Cytocompatibility of NPs is investigated using the cell viability assay. Finally, the NP suspensions are irradiated with a NIR laser to determine their effectiveness as potential materials for photothermal therapy (PTT).

A protocol is presented for the synthesis and preparation of nanoparticles consisting of electroactive polymers.

Propriedades eletroativo Polymer Nanopartículas Exhibiting fototérmicos

A method for the synthesis of electroactive polymers is demonstrated, starting with the synthesis of extended conjugation monomers using a three-step ...

Engenharia

Facile Synthesis of Worm-like Micelles by Visible Light Mediated Dispersion Polymerization Using Photoredox Catalyst

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins with the synthesis of a hydrophilic poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) homopolymer using reversible addition-fragmentation chain-transfer (RAFT) polymerization. Under mild visible light irradiation (&#955; = 460 nm, 0.7 mW/cm2), this macro-chain transfer agent (macro-CTA) in the presence of a ruthenium based photoredox catalyst, Ru(bpy)3Cl2 can be chain extended with a second monomer to form a well-defined block copolymer in a process known as Photoinduced Electron Transfer RAFT (PET-RAFT). When PET-RAFT is used to chain extend POEGMA with benzyl methacrylate (BzMA) in ethanol (EtOH), polymeric nanoparticles with different morphologies are formed in situ according to a polymerization-induced self-assembly (PISA) mechanism. Self-assembly into nanoparticles presenting POEGMA chains at the corona and poly(benzyl methacrylate) (PBzMA) chains in the core occurs in situ due to the growing insolubility of the PBzMA block in ethanol. Interestingly, the formation of highly pure worm-like micelles can be readily monitored by observing the onset of a highly viscous gel in situ due to nanoparticle entanglements occurring during the polymerization. This process thereby allows for a more reproducible synthesis of worm-like micelles simply by monitoring the solution viscosity during the course of the polymerization. In addition, the light stimulus can be intermittently applied in an ON/OFF manner demonstrating temporal control over the nanoparticle morphology.

This article describes a process for producing polymeric self-assembled nanoparticles using visible light mediated dispersion polymerization. Using low energy visible light to control the polymerization allows for the reproducible formation of self-assembled worm-like micelles at high solids content.

Síntese Facile de micelas Worm-like por luz visível Mediated Dispersão Polimerização Usando Photoredox Catalisador

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins ...

A Simple and Efficient Protocol for the Catalytic Insertion Polymerization of Functional Norbornenes

Norbornene can be polymerized by a variety of mechanisms, including insertion polymerization whereby the double bond is polymerized and the bicyclic nature of the monomer is conserved. The resulting polymer, polynorbornene, has a very high glass transition temperature, Tg, and interesting optical and electrical properties. However, the polymerization of functional norbornenes by this mechanism is complicated by the fact that the endo substituted norbornene monomer has, in general, a very low reactivity. Furthermore, the separation of the endo substituted monomer from the exo monomer is a tedious task. Here, we present a simple protocol for the polymerization of substituted norbornenes (endo:exo ca. 80:20) bearing either a carboxylic acid or a pendant double bond. The process does not require that both isomers be separated, and proceeds with low catalyst loadings (0.01 to 0.02 mol%). The polymer bearing pendant double bonds can be further transformed in high yield, to afford a polymer bearing pendant epoxy groups. These simple procedures can be applied to prepare polynorbornenes with a variety of functional groups, such as esters, alcohols, imides, double bonds, carboxylic acids, bromo-alkyls, aldehydes and anhydrides.

We describe the catalytic insertion polymerization of 5-norbornene-2-carboxylic acid and 5-vinyl-2-norbornene to form functional polymers with a very high glass transition temperature.

Um protocolo simples e eficiente para a polimerização por inserção catalítica de norbornenos funcionais

Norbornene can be polymerized by a variety of mechanisms, including insertion polymerization whereby the double bond is polymerized and the bicyclic ...

Preparation of Polyoxometalate-based Photo-responsive Membranes for the Photo-activation of Manganese Oxide Catalysts

This paper presents a method to prepare charge-transfer chromophores using polyoxotungstate (PW12O403-), transition metal ions (Ce3+ or Co2+), and organic polymers, with the aim of photo-activating oxygen-evolving manganese oxide catalysts, which are important components in artificial photosynthesis. The cross-linking technique was applied to obtain a self-standing membrane with a high PW12O403- content. Incorporation and structure retention of PW12O403- within the polymer matrix were confirmed by FT-IR and micro-Raman spectroscopy, and optical characteristics were investigated by UV-Vis spectroscopy, which revealed successful construction of the metal-to-metal charge transfer (MMCT) unit. After deposition of MnOx oxygen evolving catalysts, photocurrent measurements under visible light irradiation verified the sequential charge transfer, Mn &#8594; MMCT unit &#8594; electrode, and&#160;the photocurrent intensity was consistent with the redox potential of the donor metal (Ce or Co). This method provides a new strategy for preparing integrated systems involving catalysts and photon-absorption parts for use with photo-functional materials.

Here, we present a protocol to prepare charge transfer chromophores based on a polyoxometalate/polymer composite membrane.

Preparação de membranas de foto-sensível com base em germânio para a foto-ativação de catalisadores de óxido de manganês

This paper presents a method to prepare charge-transfer chromophores using polyoxotungstate (PW12O403-), transition metal ions (Ce3+ or Co2+), and organic ...

[(DPEPhos)(bcp)Cu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst

Our group recently reported the use of [(DPEPhos)(bcp)Cu]PF6 as a general copper-based photoredox catalyst which proved efficient to promote the activation of a broad variety of organic halides, including unactivated ones. These can then participate in various radical transformations such as reduction and cyclization reactions, as well as in the direct arylation of several (hetero)arenes. These transformations provide a straightforward access to a range of small molecules of interest in synthetic chemistry, as well as to biologically active natural products. Altogether, [(DPEPhos)(bcp)Cu]PF6 acts as a convenient photoredox catalyst which appears to be an attractive, cheap and complementary alternative to the state-of-the-art iridium- and ruthenium-based photoredox catalysts. Here, we report a detailed protocol for the synthesis of [(DPEPhos)(bcp)Cu]PF6, as well as NMR and spectroscopic characterizations, and we illustrate its use in synthetic chemistry for the direct arylation of (hetero)arenes and radical cyclization of organic halides. In particular, the direct arylation of N-methylpyrrole with 4-iodobenzonitrile to afford&#160;4-(1-methyl-1H-pyrrol-2-yl)benzonitrile and the radical cyclization of N-benzoyl-N-[(2-iodoquinolin-3-yl)methyl]cyanamide to afford natural product luotonin A are detailed. The scope and limitations of this copper-based photoredox catalyst are also briefly discussed.

[DPEPhosbcpCu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst

Detailed and general protocols are presented for the synthesis of [(DPEPhos)(bcp)Cu]PF6, a general copper-based photoredox catalyst, and for its use in synthetic chemistry for the direct arylation of C-H bonds in (hetero)arenes and radical cyclization of organic halides.

[(DPEPhos) (BCP) UC] PF6: um catalisador Photoredox cobre-baseado geral e amplamente aplicável

Our group recently reported the use of [(DPEPhos)(bcp)Cu]PF6 as a general copper-based photoredox catalyst which proved efficient to promote the ...

3D Printing and In Situ Surface Modification via Type I Photoinitiated Reversible Addition-Fragmentation Chain Transfer Polymerization

3D printing provides facile access to geometrically complex materials. However, these materials have intrinsically linked bulk and interfacial properties dependent on the chemical composition of the resin. In the current work, 3D printed materials are post-functionalized using the 3D printer hardware via a secondary surface-initiated polymerization process, thus providing independent control over the bulk and interfacial material properties. This process begins with preparing liquid resins, which contain a monofunctional monomer, a crosslinking multifunctional monomer, a photochemically labile species that enables initiation of polymerization, and critically, a thiocarbonylthio compound which facilitates reversible addition-fragmentation chain transfer (RAFT) polymerization. The thiocarbonylthio compound, known commonly as a RAFT agent, mediates the chain growth polymerization process and provides polymeric materials with more homogeneous network structures. The liquid resin is cured in a layer-by-layer fashion using a commercially available digital light processing 3D printer to give three-dimensional materials having spatially controlled geometries. The initial resin is removed and replaced with a new mixture containing functional monomers and photoinitiating species. The 3D printed material is then exposed to light from the 3D printer in the presence of the new functional monomer mixture. This allows photoinduced surface-initiated polymerization to occur from the latent RAFT agent groups on the surface of the 3D printed material. Given the chemical flexibility of both resins, this process allows a wide range of 3D printed materials to be produced with tailorable bulk and interfacial properties.

3D Printing and In Situ Surface Modification via Type I Photoinitiated Reversible Addition-Fragmentation Chain Transfer Polymerization

The present protocol describes the digital light processing-based 3D printing of polymeric materials using type I photoinitiated reversible addition-fragmentation chain transfer polymerization and the subsequent in situ material post-functionalization via surface-mediated polymerization. Photoinduced 3D printing provides materials with independently tailored and spatially controlled bulk and interfacial properties.

Impressão 3D e Modificação da superfície in situ através da polimerização da cadeia de adição reversível do tipo I fotoinitida

3D printing provides facile access to geometrically complex materials. However, these materials have intrinsically linked bulk and interfacial properties ...

Photochemical Initiation Of Radical Polymerization Reactions

Source: David C. Powers, Tamara M. Powers, Texas A&#38;M
In this video, we will carry out the photochemically initiated polymerization of styrene to generate polystyrene, which is an important commodity plastic. We will learn the fundamentals of photochemistry and use simple photochemistry to initiate radical polymerization reactions. Specifically, in this module we will examine the photochemistry of benzoyl peroxide and its role as a photo-initiator of styrene polymerization reactions. In the described experiments, we will investigate the role of wavelength, photon absorption, and excited state structure on the efficiency (measured as quantum yield) of photochemical reactions.

Iniciação fotoquímica de reações de polimerização radical

Source: David C. Powers, Tamara M. Powers, Texas A&#38;M
In this video, we will carry out the photochemically initiated polymerization of styrene to ...

JoVE Science Education

Química Inorgânica

Free-Radical Chain Reaction and Polymerization of Alkenes

The conversion of alkenes to macromolecules called polymers is a reaction of high commercial importance. The structure of the polymer is defined by a repeating unit, while the terminal groups are considered insignificant. The average degree of polymerization represents the number of repeating units in the polymer molecule and is denoted by the subscript n.
<img alt="Figure1" src="/files/ftp_upload/11773/11773_PT_Figure_1.svg" style="text-align: center; height: 60px;" />
Alkenes undergo polymerization via a free-radical mechanism involving three steps: initiation, propagation, and termination.&#160;
Radicals are generated in the initiation step by heating a small quantity of free-radical initiators such as benzoyl peroxide. The benzoyloxy radical loses CO2 and forms a phenyl radical (Ph&#183;), which adds to the double bond of the alkene to initiate the polymerization process. One of the electrons of the alkene &#960; bond pairs with one electron from the phenyl radical to form a new C&#8211;C bond.
<img alt="Figure2" src="/files/ftp_upload/11773/11773_PT_Figure_2.svg" style="text-align: center; height: 60px;" />
<img alt="Figure3" src="/files/ftp_upload/11773/11773_PT_Figure_3.svg" style="text-align: center; height: 60px;" />
<img alt="Figure4" src="/files/ftp_upload/11773/11773_PT_Figure_4.svg" style="text-align: center; height: 80px;" />
In the propagation step, the carbon radical generated in the initiation step adds to another molecule of alkene to generate a new radical. The continuous addition of alkene monomers at the radical site yields the polymer.
<img alt="Figure5" src="/files/ftp_upload/11773/11773_PT_Figure_5.svg" style="text-align: center; height: 80px;" />
The termination step of the free-radical mechanism occurs via recombination or disproportionation. In a recombination step, two growing chains form a bond at their radical sites.
<img alt="Figure6" src="/files/ftp_upload/11773/11773_PT_Figure_6.svg" style="text-align: center; height: 60px;" />
In termination by disproportionation, a &#946;-hydrogen atom is transferred from one radical to another radical center, resulting in two non-radical products.
<img alt="Figure7" src="/files/ftp_upload/11773/11773_PT_Figure_7.svg" style="text-align: center; height: 300px;" />
The free-radical polymerization of ethylene yields low-density polyethylene (LDPE), where the low density is a consequence of significant branching in the polymer chains. Articles made from polymers surround us in various forms, such as food packaging materials, plastic bags, bottles, stationery, and automotive parts.

Free-radical Polymerization Reaction of Alkenes

Reação em Cadeia de Radicais Livres e Polimerização de Alquenos

The conversion of alkenes to macromolecules called polymers is a reaction of high commercial importance. The structure of the polymer is defined by a ...

Química orgânica

Unidade 1

Reações de Alquenos

TERMOS E CONCEITOS CHAVE

Radical Chain-Growth Polymerization: Overview

Chain-growth or addition polymerization is successive addition reactions of monomers with a polymer chain. In radical chain-growth polymerization, the reaction proceeds via a free-radical intermediate. The free radical is formed from radical initiators, which spontaneously generate free radicals by homolytic fission. Organic peroxides (such as dibenzoyl peroxide, as shown in Figure 1) or azo compounds are popular radical initiators. A low concentration ratio of radical initiator to monomer is used to minimize radical coupling.
<img alt="Figure1" src="/files/ftp_upload/12920/12920_PT_Figure_1.svg" style="text-align: center; height: 75px;" />
Figure 1: The homolytic fission reaction of radical initiator dibenzoyl peroxide to generate benzoyloxy radicals and the subsequent decomposition to phenyl radicals
This free radical initiates polymerization by reacting with a monomer molecule. Unsaturated monomers are suitable for radical chain-growth polymerization; a substituent group across the unsaturated bond that stabilizes the free radical increases the reaction feasibility. Ethylene, propylene, vinyl chloride, and styrene are examples of monomers that can be polymerized via free-radical chain-growth polymerization.
The reaction between a monomer and a free radical generates a new free radical. This new radical reacts with another monomer and creates yet another free radical. The polymer chain grows as the reaction between free-radical intermediates and monomers repeats sequentially. Typically, the propagation step repeats one thousand to ten thousand times before the termination of polymerization.
Often, chain transfer reagents, such as thiol, are used to control the molecular weight (Figure 2). A chain transfer agent must be sufficiently reactive to transfer a hydrogen atom to the growing chain to terminate the polymer growth. The resultant radical must add to a double bond in the monomer to initiate polymerization.
<img alt="Figure2" src="/files/ftp_upload/12920/12920_PT_Figure_2_.svg" style="text-align: center; height: 150px;" />
Figure 2: (Top): The termination reaction of chain transfer agent thiol and a growing polymer chain; (Bottom): Subsequent reaction of thiol radical and monomer molecule to initiate polymer growth
Inhibitors are the reagents used to reduce the reactivity of radicals in the growing polymer chain. Figure 3 depicts the reaction of benzoquinone as an inhibitor.
<img alt="Figure3" src="/files/ftp_upload/12920/12920_PT_Figure_3.svg" style="text-align: center; height: 200px;" />
Figure 3: The reaction between chain inhibitor benzoquinone and a growing polymer chain to generate a less reactive free radical

Polimerização Radicalar de Crescimento em Cadeia: Visão Geral

Chain-growth or addition polymerization is successive addition reactions of monomers with a polymer chain. In radical chain-growth polymerization, the ...